The present invention relates generally to stabilizing motions such as roll and pitch imparted to marine vessels during seawater travel.
Marine vessels such as naval ships often slow down during travel in rough seas so as to reduce seawater wave induced motions such as roll and pitch, because excessive amounts of such motions may seriously degrade combat readiness, adversely affect performance of on-board systems such as weapons and have other deleterious affects. Various methods have therefore been developed to reduce roll and pitch including use of active devices. Such active devices applied for example to fins, gyros, tanks and rudders often introduce cavitation, vibration and tip vortex problems at high travel speeds. It is therefore an important object of the present invention to provide active devices for inducing corrective roll and pitch motions on marine vessels during seawater travel under rough wave conditions for motion stabilization purposes without introducing the problems heretofore experienced.
In accordance with the present invention, a motion stabilizer system includes a pair of depressors in sliding contact with each other disposed on the stem of a marine vessel between the port and starboard sides thereof, for displacement between positions retracted from the seawater and deployed positions immersed therein. Lower end portions of such depressors immersed in the seawater in the deployed positions divert and smooth exit flow of the seawater from the stem between side plates along curved flow path surfaces during vessel travel. Such diversion of the exit flow increases dynamic forces heretofore induced by such exit flow. One of such depressors, on either the port or starboard side, is deployed by an appropriate distance into the seawater under motion stabilization control to produce increased hydrodynamic forces in response to correspondingly diverted exit flow of the seawater from the stem for imparting corrective roll on the vessel in one angular direction to cancel roll otherwise imparted by the seawater under rough wave conditions. Both of the depressors are simultaneously deployed on the other hand under stabilization control for immersion into the seawater by some other appropriate distance to produce hydrodynamic forces in response to exit flow which impart corrective pitch on the vessel for cancellation of pitch otherwise resulting from seawater flow under rough conditions.